I generally tend to go for Archlinux, because its pretty simple to set up a very lightweight system right out of the box, and the rolling release means that I never have to reinstall or deal with a huge update. I've never had any stability issues with it personally, but it does happen, particularly if you tend to retain older versions of a lot of packages for whatever reason. Debian would probably be a good choice in that case. My experience stops at Linux though, I haven't used a whole lot of *BSD.
You can always wait for Stali I suppose. :)
